The present invention relates to a dynamometric key and more particularly to a key of this type intended to ensure tightening and loosening of an insert on a dental handpiece.
Dynamometric keys used in industry, which are adapted to deliver considerable tightening and even loosening moments, are known. Such dynamometric keys are constituted by complex mechanical elements which are easy to employ in devices of respectable volume but which are particularly difficult and expensive to manufacture as soon as it is desired to transpose them to a smaller scale.
U.S. Pat. No. 6,021,694 in particular discloses a dynamometric key intended for surgical use which is essentially constituted by a tubular element containing a linear helicoidal spring of which the level of compression is determined by means of an adjusting screw. This compression spring acts by friction on the outer part of the ball bearing housing, which retransmits to the end of the key a moment determined by its level of friction. Such a device is difficult to use in certain domains of applications and in particular in that of the dental domain by reason of the considerable lever arm constituted by this device which gives it a large volume which is incompatible with the techniques used.